Acid-Base Balance

pH

• Measures the acidity or alkalinity of a solution

pH (Normal pH)

• pH 7.35 - 7.45

pH (Acidosis)

• Large number of H ions =

  • Decreased pH

  • < 7.35

  • Acidosis

pH (Alkalosis)

• Small number of H ions =

  • Increased pH

  • > 7.45

  • Alkalosis

pH (Acid)

• Compound that allows hydrogen ions to break free

• Decreased pH

pH (Base)

• Compound that binds with hydrogen ions

• Increased pH

Regulation

• Chemical Buffer Systems

  • Keeps the pH relatively constant

• Carbonic Acid - Bicarbonate Buffer System

  • The system that we monitor clinically

  • Carbonic acid (Acid) = H2CO3 (CO2 & H20)

  • Bicarbonate (Base) = HCO3

• Phosphate Buffer System

• Protein Buffer System

Regulation (Carbonic Acid-Bicarbonate Buffer System)(Respiratory Control)

• Respiratory control (CO2 changes)

  • Less you breathe = Less CO2 comes out = More Acid

  • Low Resp. rate = Increase Acid

  • Increased Resp. rate = Less acid = Less CO

• Makes changes seconds to minutes

• pH Acidic (<7.35) → Inc. resp. rate & depth

  • To get rid of CO2 = Dec. Acid

• pH Alkaline (>7.45) → Dec. resp. rate & depth

  • To save CO2 = Inc. Acid

Regulation (Carbonic Acid-Bicarbonate Buffer System)(Renal Regulation)

• Renal Regulation (Metabolic HCO3 changes)

• Controls hydrogen ions & Bicarbonate

• Makes changes in several hours to days

• pH Acidic (<7.35)

  • H+ excreted in urine

• pH alkaline (>7.45)

  • HCO3 excreted in urine

Acid-Base Disturbances

• Metabolic Acidosis

  • Diarrhea (Losing BCO3)

• Respiratory Acidosis

  • RR is slow

• Metabolic Alkalosis

  • Vomiting

• Respiratory Alkalosis

  • RR is fast

Acid-Base Disturbances (Resp. Acidosis & Alkalosis)

• Resp. Acidosis & Alkalosis have a root cause:

  • In something w/ ventilation &/or alveoli gas exchange

• Retain CO2 = Acidic

  • Ex: COPD, Asthma

• Acidosis = Slow RR

  • Cause: OSA, Head trauma

• Alkalosis = Fast RR

  • Body: Panic attack/ Hyperventilation

  • Rapidly blows off acid → base

• Too much base → Body needs to breathe slower to retain CO2/ rebreathe it in

• Too much acid → Body breathes faster to blow off CO2

Acid-Base Disturbances (Metabolic Acidosis & Alkalosis)

• Metabolic Acidosis or Alkalosis have a root cause:

  • In something metabolism related

  • In the body NOT respiratory

  • Urine or stomach acid

• Renal injury:

  • Can’t excrete urine

  • Acidic state

  • Acidotic (High in H ions)

• Vomiting:

  • Loss of stomach acid

  • Leaves alkalosis (Base)

• Diarrhea:

  • Poop out all of the base

  • Acidotic state

Acidosis

• Abnormal increase in hydrogen ion concentration

  • Accumulation of excess acid

  • or

  • Loss of bicarbonate = Loss of base (Inc. acidity)

• An acidotic patient will immediately have hyperkalemia

Metabolic Acidosis

• Accumulation of excess metabolic acids or bicarbonate is lost

Metabolic Acidosis (Etiology)

• Salicylate intoxication

  • Cause: Too much Aspirin

  • Tx: Dialysis

• Hypoxia, shock, sepsis → lactic acid

• DKA → ketoacidosis

  • Insulin

  • Fluids/ electrolytes

  • NPO

• Renal failure

  • Can’t reabsorb or excrete acid

  • Dialysis

• Loss of bicarbonate

  • Diarrhea

• All metabolic acidoses have Kussmals resp.